LeetCode54

[jhm9595]

Time Complexity : O(N)

[bigelephant29]

(1) Add a class "Direction".

class Direction {
    private int r; // Each step for row-direction
    private int c; // Each step for column-direction
    public int getR() {
        return r;
    }
    public int getC() {
        return c;
    }
}

You can initialize a static array of Direction with values

(0, 1)
(1, 0)
(0, -1)
(-1, 0)

(2) Add a util function outOfBound(int[][] matrix, int r, int c)

private boolean outOfBound(int[][] matrix, int r, int c) {
    return r >= 0 && c >= 0 && r < matrix.length && c < matrix[0].length;
}

If you have (1) and (2), the implementation in your while loop can be simplified into:

int nextR = r + directions[currentDirection].getR();
int nextC = c + directions[currentDirection].getC();

if(outOfBound(matrix, nextR, nextC) || traceMap[nextR][nextC] == 1) {
    currentDirection = (currentDirection + 1) % 4;
} else {
    r = nextR;
    c = nextC;
    result.add(matrix[r][c]);
    traceMap[r][c] = 1;
}